Ethylene glycol based antifreeze formulations may be inhibited with inorganic additives, e.g., alkali metal borates and phosphates, which phosphate-borate type ethylene glycol based antifreeze formulations have excellent corrosion preventive properties when used in cooling systems associated with conventional cast iron internal combustion engines. In efforts to reduce weight and maximize fuel efficiency, there is a trend toward use of aluminum engine components, particularly aluminum cylinder heads.
It has been observed that when phosphate-borate ethylene glycol based antifreeze formulations are used in cooling systems of internal combustion engines having aluminum components, e.g. cylinder heads, aluminum corrosion products reach a solubility maximum in the antifreeze and precipitate out in the radiator section of the cooling system resulting in engine overheating due to diminished heat transfer in the radiator.